Multi-component, extruded vegetation cutting line

ABSTRACT

A multicomponent monofilament cutting line includes a first component material and a second component material, the same or different in chemical structure from the first component material and extruded separately from the first component material. The second component material provides the cutting line with cutting edges and has increased wear resistance properties and increased abrasion resistance properties compared to those same properties of the first component material. The monofilament cutting line for a rotary trimmer for cutting vegetation preferably includes a first component material having a specific gravity of about 1.15 g/cc or less; and a second component material having a specific gravity greater than 1.15 g/cc. Notably, the multi-component, monofilament cutting line itself has increased wear resistance and increased abrasion resistance as compared to a single component monofilament cutting line employing one of either the first or second component materials.

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/834,221, filed Apr. 12, 2001, which claims the benefit ofU.S. provisional application No. 60/196,413, filed Apr. 12, 2000.

TECHNICAL FIELD

[0002] This invention relates generally to a bicomponent ormulti-component extruded monofilament used as a vegetation cutting linefor a rotating trimmer. More particularly, the invention relates to anextruded monofilament cutting line having wear resistant edges, and, ina particular embodiment, replenishing wear-resistant edges imbeddedwithin an abrasion or non-abrasion resistant sheath. The presentinvention also relates to an extruded monofilament cutting linecontaining an embedded grit or abrasive material. The present inventionfurther relates to an extruded monofilament cutting line containing ahigh density material to increase the force of the impact between thecutting line and the vegetation.

BACKGROUND OF THE INVENTION

[0003] Vegetation cutting devices are well known in the art. Thesedevices, including rotating trimmers, typically employ monofilamentcutting or trimming line for cutting overgrown vegetation such as grassand weeds, edging lawns around borders and concrete, and trimming grassin places that are hard to reach with lawn mowers. Smaller lines aretypically used for trimming grasses, while fine blades and larger linesare typically used for cutting larger stalks of weeds or grasses andheavy growth.

[0004] Shaped monofilament cutting lines were introduced in the late1980's and have been shown to have significantly improved the cuttingquality of weeds and like vegetation. By the term “shaped”, it is meantthat the cutting line has a cross-sectional configuration other thanround, which is the cross-sectional configuration of conventionalmonofilament cutting lines. More particularly, cross-sectional shapesother than round have been used because the edges or corners created bythose shapes provide for cleaner cuts of the grass or weeds, resultingin less tearing of the blades of grass. In turn, less tearing of theblades of grass desirably results in less browning of the grass endsafter cutting.

[0005] There are, however, at least two drawbacks to using these shapedmonofilament lines. First, some of the shapes tend to damage the head ofthe rotating trimmer when it comes out of the head, since the outermostsurface of the line is not smooth. Vice versa, the head may damage thetrimmer line. Second, the shapes have been known to become worn duringuse, thereby reducing their improved effectiveness in the cut quality ofthe vegetation. That is, some of the edges and corners created by thecross-sectional shapes of the cutting line wear off, leaving a somewhatrounded strand that is less effective in cutting vegetation.

[0006] Various attempts have been made heretofore to overcome thisproblem. For example, U.S. Pat. No. 5,430,943 provides ashape-within-a-shape monofilament line. The patent proposes the use of acutting element having a shaped inner cutting edge that is exposed foruse after the outermost cutting edge has been worn away. However, thisconcept has proved to be limited by the number of shapes that can bedesigned, and it only uses a single component material in theconstruction of the monofilament cutting line.

[0007] Others have attempted to provide mono-component cutting lineswith improved wear resistant properties. Ideally, blended resins andadditives extruded to produce the cutting lines are selected to maximizethe wear resistance and the impact properties of the monofilamentcutting line. Unfortunately, it has been found that materials thatprovide the best results with respect to wear resistance do notgenerally provide the best results with respect to impact properties.Thus, a compromise is generally made to balance the performance of themonofilament cutting line. Additionally, it has been found that resinsthat provide the best wear resistance also have properties which causedefects such as voids, excessive out-of-roundness, or splitting, of themonofilament during extrusion.

[0008] Thus, the need exists for a monofilament cutting line exhibitingimproved wear resistance as compared to other monofilament cutting lineswhile maintaining good impact properties, and, if desired, that iscapable of protecting the head of the rotating trimmer.

SUMMARY OF INVENTION

[0009] It is therefore, an object of the present invention to provide amulti-component, extruded monofilament cutting line.

[0010] It is another object of the present invention to provide amulti-component monofilament cutting line having improved wearresistance and good impact properties.

[0011] It is still another object of the present invention to provide amulti-component monofilament cutting line that will neither damage norbe damaged by the head of the rotating trimmer in which it may beemployed.

[0012] It is yet another object of the present invention to provide amulti-component monofilament cutting line having a smooth fiber surfacewhen coming out of the trimmer head.

[0013] It is still another object of the present invention to provide ashaped multi-component monofilament cutting line that will maintain itscross-sectional configuration for a longer period of use.

[0014] It is yet another object of the present invention to provide amulti-component monofilament cutting line which can offer improved wearresistance without excessive voids, splitting or out-of-roundness.

[0015] It is a further object of the present invention to provide amulti-component monofilament cutting line with replenishing edges.

[0016] It is still a further object of the present invention to providea multi-component monofilament cutting line having inner edges and outeredges, wherein the inner edges may be exposed after the outer edges havebeen worn down.

[0017] It is yet a further object of the present invention is to providea multi-component monofilament cutting line containing an embedded gritor abrasive material.

[0018] It is yet an additional object of the present invention toprovide a multi-component monofilament cutting line containing a highdensity material to increase, during use, the force of impact betweenthe cutting line and vegetation.

[0019] At least one or more of the foregoing objects, together with theadvantages thereof over the known art relating to monofilament cuttinglines, which shall become apparent from the specification that follows,are accomplished by the invention as hereinafter described and claimed.

[0020] In general, aspects of the present invention are accomplished byproviding an extruded monofilament cutting line for a rotary trimmer forcutting vegetation including a first component material; and a secondcomponent material, the same or different in chemical structure from thefirst component material and extruded separately from the firstcomponent material. The second component material provides the cuttingline with cutting edges and has increased wear resistance properties andincreased abrasion resistance properties compared to those sameproperties of the first component material.

[0021] Other aspects of the invention are provided by a monofilamentcutting line for a rotary trimmer for cutting vegetation comprising afirst component material having a specific gravity of about 1.15 g/cc orless; and a second component material having a specific gravity greaterthan 1.15 g/cc.

[0022] Still other aspects of the present invention are accomplished byproviding a multi-component, monofilament cutting line for a rotarytrimmer for cutting vegetation including at least a first componentmaterial; and at least a second component material, the same ordifferent in chemical structure from the first component material butnot blended with the first component material and extruded separatelyfrom the first component material. The second component materialprovides the cutting line with cutting edges. Notably, themulti-component, monofilament cutting line has increased wear resistanceand increased abrasion resistance as compared to a single componentmonofilament cutting line employing one of either the first or secondcomponent materials.

[0023] Still other aspects of the present invention are accomplished byproviding a monofilament cutting line including a first componentmaterial having an abrasive filler and/or a second component materialproviding a sheath surrounding the first component material.

[0024] Exemplary multi-component monofilament cutting linesincorporating the concepts of the present invention are shown by way ofexample in the accompanying drawings without attempting to show all thevarious forms and modifications in which the invention might beembodied, the invention being measured by the appended claims and not bythe details of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a representative cross-sectional view of one embodimentof the multi-component monofilament cutting line of the presentinvention;

[0026]FIG. 2 is a representative cross-sectional view of anotherembodiment of the multi-component monofilament cutting line of thepresent invention.

[0027]FIG. 3 is a representative cross-sectional view of a thirdembodiment of the multi-component monofilament cutting line of thepresent invention;

[0028]FIG. 4 is a representative perspective view of a fourth embodimentof the multi-component monofilament cutting line of the presentinvention, further showing a cross-section of the cutting line;

[0029]FIG. 5 is a representative perspective view of a fifth embodimentof the multi-component monofilament cutting line of the presentinvention, further showing a cross-section of the cutting line;

[0030]FIG. 6 is a representative cross-sectional view of a sixthembodiment of the multi-component monofilament cutting line of thepresent invention;

[0031]FIG. 7 is a representative cross-sectional view of a seventhembodiment of the multi-component monofilament cutting line of thepresent invention; and

[0032]FIG. 8 is a representative segmented, perspective view of aneighth embodiment of the multi-component monofilament cutting line ofthe present invention having each layer of the multi-component cuttingline partially striped away.

DETAILED DESCRIPTION OF THE INVENTION

[0033] As noted hereinabove, the present invention is directed towardthe production of a multi-component, monofilament cutting line for usein rotary grass trimming machines. The production of monofilamentcutting line according to the present invention involves the use ofbicomponent or multi-component extrusion technology. That is, in theproduction of the monofilament, two or more separate resins may beextruded separately (using separate extruders) into and through anintricately designed die head of the extrusion machine to which eachextruder is operatively connected, to form a single monofilament of twoor more separate components.

[0034] Typically, the monofilament will be layered, having a core-sheathor core-mantle(s)-sheath configuration, although the present inventionis not necessarily limited thereto. The core-sheath orcore-mantle(s)-sheath construction of the monofilament can besymmetrical, i.e., layered, or asymmetrical, e.g., as a bivalve ormultivalve arrangement. Other arrangements of two or more components arealso contemplated and are not necessarily limited by this disclosure.For example, side-by-side configurations, islands-in-the-streamconfigurations, and multi-legged configurations are also believedsuitable. For ease of discussion, however, the core-mantle-sheathconfiguration will be generally discussed.

[0035] The monofilament itself can be solid or hollow, and may have around or another shaped cross-sectional configuration. The core,mantle(s) or sheath each may also have any cross-sectional configurationknown in the art unless expressly provided otherwise. Moreover, each ofthe core, the mantle, or the sheath may include a filled or unfilledpolymer, which may be commonly or not commonly used in the manufactureof monofilament cutting line, depending upon the structure andproperties desired of the monofilament and each of its components. Itwill also be understood that, where a bicomponent extrusion technique isemployed, there will be no mantle(s).

[0036] In a first embodiment shown in FIG. 1, the cross-sectionalconfiguration of a multi-component monofilament cutting line, generallydenoted by the numeral 10, is presented. The cutting line 10 includes afirst component material 12 and a second component material 14 providingcutting edges 16. For apparent reasons, in the embodiment of FIG. 1,first component material 12 may be considered the core of the cuttingline 10, while second component material 14 may be considered thesheath. Preferably, first component material 12 is a tough, impactresistant material, and second component material 14 is a materialhaving substantial wear and abrasion resistant properties so as toprovide cutting line 10 with hard, wear resistant cutting edges 16.

[0037] It will be appreciated that while, in this embodiment, secondcomponent material 14 may be referred to as a “sheath,” there is norequirement that the second component material 14 completely encompassor surround the first component material 12, providing a “core”. Cuttingedges 16 may be separately spaced around first component material 12,such as shown in FIG. 1, and extend along the length of themonofilament, with first component material 12 extending between thevarious cutting edges 16 with respect to the outside surface of themonofilament cutting line 10. Thus, monofilament cutting line 10 may beconsidered “striped” with wear resistant, second component material 14extending along the longitudinal axis proximate cutting edges 16 of themonofilament 10. Still further, the second component may be limited andused only as the cutting edges themselves, the rest of the cutting linebeing made from the first component material or other materials.

[0038] Notably, monofilament cutting line according to the presentembodiment may have any cross-sectional configuration known in the artas providing suitable cutting edges for cutting grasses and otherovergrown vegetation. A number of alternative shaped monofilamentdesigns are shown in U.S. Pat. No. 5,430,943; 4,869,055, D379,419,D379,052, D376,739, D376,516, D376,079, D376,078, D365,734, D364,079,D358,535, and D349,634, all of which are incorporated herein byreference. Generally, any cross-sectional shape other than round may beemployed for this embodiment of the present invention although,preferably, distinct cutting edges are provided. Moreover, as discussedabove, the second component material can form a sheath surrounding thefirst component material or only form that part of the cutting lineforming the cutting edges.

[0039] As mentioned above, multi-component cutting line 10 includes acore first component material 12 comprising essentially any resinmaterial with good impact properties and reasonably good wear resistantproperties. This material is preferably tough and may include, but isnot necessarily limited to, polyolefins, POLYIMIDES, polyurethanes, andcopolymers, terpolymers, and ionomers thereof, as well as mixtures orblends thereof. Preferred first component materials 12 suitable as acore include nylon 6 and nylon copolymers and terpolymers, including anyone or more of nylon 6/66, 6/69, 6/636, 6/11, 6/12, 6/612 and 6/610.Polymers commonly used in the manufacture of cutting lines areparticularly useful for the core first component material 12 in thisembodiment.

[0040] First component material 12 may be filled or unfilled, and, forpurposes of the present embodiment, the term “component material” is tobe understood as broadly covering both filled and unfilled materials. Iffilled, first component material 12 may be a blend of polymer and fillerand include any known filler suitable for use in the material beingfilled. For example, fillers may include mineral fillers and salts suchas, but not limited to, silica, mica, carbon black, talc or aluminumpowder. These fillers are generally added to decrease cost.

[0041] Other fillers may include high molecular weight fillers thatincrease the density of the core as explained hereinbelow. Essentially,these fillers increase the mass of the cutting line, thereby impartinggreater impact to the cutting line as compared to single componentmonofilament lines.

[0042] Similarly, fillers such as clay may be added to impart otherphysical characteristics to the component material. Clay generallyimparts toughness to the material.

[0043] Still other fillers may be added for different reasons. Forexample, first component material 12 may include cross-linking additivessuch as functionalized epoxy resins and the like to chemically linkfirst component material 12 to second component material 14.

[0044] Second component material 14 constitutes the cutting edges 16 ofmonofilament cutting line 10. Generally, the material selected forsecond component material 14 should be extrudable, yet impart betterwear resistance and better abrasion resistance than the polymerscommonly used in rotary trimmer lines. Essentially any known, highabrasion resistant, high wear resistant material may be used. Byproviding a material that provides greater wear resistance and greaterabrasion resistance, the overall performance and durability of thecutting line in cutting blades of grass or other vegetation is improved.That is, use of a second component material having increased wearresistance and increased abrasion resistance as compared to the firstcomponent material, improves the wear resistance and abrasion resistanceof the multi-component, monofilament cutting line as compared to otherknown single component monofilament cutting lines as well.

[0045] It is generally preferred that the polymer(s) employed in theproduction of second component material 14 be comparable or compatiblewith the polymer(s) employed in first component material 12. Thus, thesecond component material 14 may be the same or different in chemicalstructure as the first component material 12. However, second componentmaterial 14, providing cutting edges 16 to monofilament cutting line 10,should have better wear and abrasion resistant properties as compared tofirst component material 12. Thus, second component material 14 and,thus, cutting edges 16, may comprise the same or different type ofmaterial as first component material 12, and may also be filled orotherwise modified with one or more additives, as above. To obtainimproved wear and abrasion resistance properties when the same materialcomponents are used, one of the component materials must be processeddifferently or processed through the extruder differently. This may bedone with a different extrusion head, or using different draw ratios, orany other means known in the art.

[0046] It will also be appreciated that the second component material 14can be made from plastics such as, but not limited to, polycarbonate,ionomer resins such as Surlyn®, and polyphenylene sulfide (PPS), or canbe made from more conventional polymers with various fillers oradditives to provide improved wear and abrasion resistant properties.Suitable examples of such abrasion-resistant and/or wear-resistantadditives include any of the plastics contemplated above, metal,metallic materials, ceramic materials, glass fibers including choppedfibers, fine denier chopped thermoplastic fibers, cross-linkers,amorphous resins or any other material that can be suitably extrudedwith or without conventional polymers and provide improved abrasion orwear resistance.

[0047] Typical levels of abrasion resistance or wear resistance differsignificantly depending upon the material used, and the cross-sectionalconfiguration of the cutting line itself. Thus, determining quantitativelevels for these properties for prior art cutting lines is insignificantunless or until compared to counterpart multi-component monofilamentcutting lines of the present invention. However, it is desirable thatthe novel multi-component monofilament cutting lines of the presentinvention provide greater wear resistance and abrasion resistance thanthe prior art single component monofilament cutting lines.

[0048] To improve upon the prior art, the present embodiment of amulti-component cutting line according to the present invention employsmore than one component material, and particularly employs, at thecutting edges of the cutting line, a component material having betterwear and abrasion resistant properties than component material employedin areas that are not proximate the cutting edges of the cutting line.

[0049] For example, in FIG. 1, as has already been mentioned, secondcomponent material 14 may have better wear and abrasion resistantproperties than first component material 12, so as to provide a cuttingline in 10 with increased structural integrity at those areas where itis most needed, mainly, proximate the intended cutting edges of thecutting line. On the other hand, the impact strength of the secondcomponent material 14 may or may not be that of the first componentmaterial.

[0050] Morever, due to considerations of material costs or otherpractical design considerations, the component material providing thecutting line with cutting edges, such as second component material 14 ofFIG. 1, may optionally be provided only at areas proximate the cuttingedges. In other words, if higher cost is an important consideration,extruding the second component material 14 (in this embodiment, deemedthe more expensive material) so as to only just cover cutting edges 16at the tips thereof may be appropriate.

[0051] It will be appreciated that other problems, including thoseassociated with the use of certain wear resistant materials, such asvoids, splitting and out-of-roundness, can now be more easily avoided.For example, any voids existent in second component material 14, as aresult of employing certain wear resistant materials, can be readilyfilled with first component material 12 during extrusion, and viceversa. The problems with splitting and out-of roundness are alsoessentially eliminated due to the fact that smaller diameter anddifferently shaped components are being utilized for extrusion intomulti-component monofilament cutting line 10.

[0052] It will also be appreciated that the extruded multi-componentmonofilament cutting line 10 produced according to the present inventionshould be flexible enough to be used as vegetation cutting line. Whilesome materials chosen for second component material 14 may beparticularly hard and wear resistant, they should have some flexibilityor monofilament cutting line 10 must provide a sufficient amount offlexible first component material 12 to compensate for the lack offlexibility of second component material 14. Moreover, it has been foundthat some polymeric materials, while having increased resistance to wearand abrasion, do not impart great impact strength. If such a material isused, it may be desirable to employ a first component material 12 havingimproved impact strength as compared to that of the prior art or thesecond component material 14.

[0053] In practice of the present invention, delamination of the secondcomponent material 14 from first component material 12 could be aconcern. Adhesion between the component materials 12, 14 can be improvedby mechanical interlocking or by improving the chemical interactionbetween them. Mechanical interlocking can be conducted at the die headof the extrusion process wherein first and second component materials12, 14 can be separately extruded in such a manner that, upon formingmonofilament cutting line 10, the component materials 12, 14 aremechanically locked to one another. For example, second componentmaterial 14 may be extruded to include a triangular flange extendingtoward first component material 12, while first component material 12 isextruded to include a complementary triangular recess for receiving theflange. Of course, it will be understood that many other techniquescould be used to mechanically interlock the components.

[0054] Bonding of first and second component materials 12, 14, viachemical interaction, can be achieved through a number of alternativemethods. For example, coupling agents may be incorporated into thecomposition of both of the extruded component materials 12, 14.Alternatively, adhesive-type additives, such as polyamide terpolymers ordimer acid-based POLYIMIDES, could be added to one or both of thecomponent materials 12, 14. Still further, additives having ionicfunctionalities, e.g., nylon ionomers, could be added to either or bothcomponent materials 12, 14. Each of these methods are believed to beknown in the art, and any other method suitable for bonding thecomponent materials 12, 14 together without affecting the desiredphysical properties of the resultant monofilament cutting line 10 wouldbe suitable.

[0055] Thus, it should be evident that multi-component monofilamentcutting line 10 of the present invention is highly effective inproviding both good impact properties, as provided by first componentmaterial 12, and excellent wear and abrasion resistance properties, asprovided by second component material 14. Problems with voids, splittingand excessive out-of-roundness are also avoided.

[0056] It is to be understood that additional layers of material,preferably with differing levels of wear and abrasion resistance as wellas impact properties, may be employed between the “core” of firstcomponent material 12 and “sheath” of second component material 14.These additional component materials can be extruded via a differentextruder but through the same die head as the first and second componentmaterials 12, 14. Furthermore, the additional component material(s)could also provide cutting edges such that a cutting edge “striped”along the longitudinal axis of the “core” of first component material 12may be different from that of another cutting edge material “striped”along the same longitudinal axis of first component material 12. When anadditional component material is employed, it is possible that it may beconsidered a “mantel” layer if it is substantially placed between a corelayer and a sheath layer of component material, such as componentmaterials 12 and 14. This concept of a mantel layer should be readilyconceivable to those of ordinary skill in the art, and it is disclosedmore fully hereinbelow with respect to other embodiments of the presentinvention.

[0057] In a second embodiment, it is envisioned that a multi-componentmonofilament cutting line with renewable cutting edges could bedesigned. This embodiment of a monofilament cutting line is exemplifiedin FIG. 2, and is designated generally by the numeral 20. Monofilamentcutting line 20 includes first component material 22 and secondcomponent material 24, both of which may be comprised of materials asdescribed hereinabove with respect to first component material 12 andsecond component material 14, respectively. Thus, second componentmaterial 24, providing edges 26, 27, and 28, describe more fully below,has better wear and abrasion resistant properties than first componentmaterial 22, and such wear and abrasion resistant properties preferablyprovide for a cutting line that also has improved wear and abrasionresistance properties which are superior to those of a single componentcutting line.

[0058] The main distinction between the embodiment of FIG. 2 and that inFIG. 1 concerns the provision of exterior cutting edges 26, firstrecessed edges 27, and second recessed edges 28 within the shape ofsecond component material 24.

[0059] As with second component material 14 in FIG. 1, second componentmaterial 24 is a hard, wear resistant material, serving to prolong thelife of monofilament cutting line 20. The embodiment of FIG. 2 providesthe added benefit of having renewable cutting edges. Particularly, asexterior cutting edges 26 become worn, first recessed edge 27 is morefully exposed and functionally replaces exterior cutting edge 26.Likewise, when first recessed edge 27 becomes worn, second recessed edge28 is more fully exposed and functionally replaces first recessed edge27. The embodiment for FIG. 2 is understood as having “renewable”cutting edges.

[0060] The “stepped” shape of second component material 24 is not theonly shape that will provide a monofilament cutting line with renewablecutting edges. Rather, various shapes providing renewable cutting edgeswill be readily apparent, and the present invention is not to be limitedto or by any particular renewable cutting edge design. Notably, U.S.Pat. No. 5,430,943 discloses a number of cutting line designs that wouldprovide renewable cutting edges, and relevant portions of that patent,relating to renewable cutting edges, are incorporated herein byreference. The main difference between that patent and the presentinvention is the fact that the present invention conceives of the use ofa multicomponent design, whereas the patent does not.

[0061] Continuing, as aforementioned, shaped monofilament cutting linestend to damage the head of a rotating trimmer because the outer mostsurface of the cutting line is not smooth. The opposite may also betrue, namely, that the head of the rotating trimmer may damage thecutting line. Providing cutting edges of increased wear and abrasionresistant material may serve to magnify this problem. Thus, it may bedesirable to provide the wear and abrasion resistant cutting edges in anmantel layer that is surrounded by a sheath that serves to protect thecutting line and trimmer head from damaging one another.

[0062] For example, in a third embodiment, as shown in FIG. 3, theconcept, of a multi-component monofilament cutting line having a tough,impact resistant core provided by a first component material and hard,wear resistant cutting edges provided by a second component material ismaintained and, thus, like parts as in FIG. 1 receive like numerals. Inthis embodiment however, the monofilament, denoted generally by thenumeral 30, includes a third component material 32 that surrounds andembeds the second component material 14 and the first component material12. Third component material 32 acts as a buffer between the cuttingedges 16 of the monofilament 30 and the head of the rotary trimmer inwhich it is used, such that the opening on the head of the rotarytrimmer does not become worn or abraded from the constant release ofcutting line 30 therefrom.

[0063] In a preferred embodiment, third component material 32 issufficiently brittle and/or non-abrasion resistant that, upon use ofcutting line 30 to cut vegetation, the outer sheath of third componentmaterial 32 quickly degrades or breaks away, leaving the hard secondcomponent material 14 and its cutting edges 16 (now considered the“mantle” in FIG. 3) for cutting the grasses. In this embodiment, thirdcomponent material 32 is preferably prepared from an abrasion ornon-abrasion resistant material, which may be softer than the othercomponents and may degrade quicker than the other components. Forexample, third component material 32 may be prepared from a lowmolecular weight nylon or other polymer such as a low molecular weightpolyolefin, e.g., polypropylene. Third component material 32 may have around or shaped outer cross-sectional configuration, the importantconsideration being that the smoothness of third component material 32prevents wear on the opening of the head of the rotary trimming machine.Notably, this smooth sheath concept can be practiced within anyembodiment of the present invention. For example, a smooth sheath couldbe provided around second component material 24 of the recessed edgesembodiment shown in FIG. 2.

[0064] In yet another embodiment, the core-sheath concept (when thereare two component materials) or core-mantle-sheath concept (when thereare at least three component materials) is maintained, but this time thelayers of the extruded monofilament from sheath to core are preferablyprepared with progressively harder, i.e., more wear resistant,materials. That is, the outermost sheath (e.g., third component material32 of FIG. 3 or second component material 14 of FIG. 1) is preferablyextruded from polymers or other known materials commonly used in themanufacture of monofilament cutting line, while the core (e.g., firstcomponent material 12 of FIGS. 1 or 3) and/or mantle(s) (e.g., secondcomponent material 14 of FIG. 3), if any, are preferably extruded fromharder, more wear resistant materials, including those materialsdescribed hereinabove with respect to second component material 14 or 24in the embodiments of FIGS. 1-3. This would allow the edges of theharder, embedded shaped layers to be exposed as the layer above it isworn away. The result is a cutting line that continually presents sharpedges for cleanly cutting grasses and other vegetation.

[0065] A core-sheath embodiment is depicted in FIG. 4, wherein themonofilament cutting line is designated generally by the numeral 40.Cutting line 40 includes a first component material 42, which isuniquely shaped and provides the core of cutting line 40. Secondcomponent material 44 surrounds first component material 42, therebyproviding a sheath to cutting line 40. As mentioned hereinabove, in thisembodiment of the present invention, the layers of cutting line 40 fromsheath (i.e. second component material 44) to core (i.e. first componentmaterial 42) are prepared from progressively harder and more wearresistant materials. Notably, cutting line 40 of FIG. 4 also serves toconvey the understanding that the present invention is not to be limitedto a particular cross-sectional shape of any individual component withina multi-component monofilament cutting line, inasmuch as first componentmaterial 42, which is a core in the present embodiment, has a veryunique shape, and provides useful exterior cutting edges 46 as well asrecessed cutting edges 48.

[0066] Referring now to FIG. 5, a core-mantel-sheath embodimentaccording to the above disclosure is depicted. Therein, multi-componentmonofilament cutting line 50 is shown having first, second, and thirdcomponent materials 52, 54, and 56, respectively. The outer most sheath(i.e. third component material 56) is preferably extruded from polymersor other known materials commonly used in the manufacture of cuttinglines while the mantel (i.e. second component material 52) is extrudedfrom a harder, more wear resistant material, and the core (i.e. firstcomponent material 52) is extruded from material that is even harder andmore wear resistant than second component material 54. Thus, as cuttingedges 58, are worn away, the embedded cutting edges 60 are exposed, and,likewise, as embedded cutting edges 60 are worn away, cutting edges 62,are exposed. It should be readily appreciated, therefore, that cuttingline 50 continually presents sharp edges for cleanly cutting grasses andother vegetation.

[0067] To improve upon the prior art, the present embodiment of amulti-component cutting line according to the present invention employsmore than one component material, and particularly employs, at thecutting edges of the cutting line, a component material having increasedwear and abrasion resistant properties than component material employedin areas that are not proximate the cutting edges of the cutting line.For example, in FIG. 1, as has already been mentioned, second componentmaterial 14 has better wear and abrasion resistant properties than firstcomponent material 12, so as to provide a cutting line in 10 withincreased structural integrity at those areas where it is most needed,mainly, approximate the intended cutting edges of the cutting line.Thus, the component material that provide the cutting edges to thecutting line aid in providing a cutting line which is superior in wearand abrasion resistance properties to conventional single component,monofilament cutting line. The first component layer provides neededimpact strength similar to many component materials of prior art.Notably, due to considerations of material costs or other practicaldesign considerations, the component material providing the cutting linewith cutting edges, such as second component material 14 of FIG. 1, mayoptionally be provided only at areas proximate the cutting edges.

[0068] Although the embodiments hereinabove described are taught ascontaining either first and second component materials or first, second,and third component materials, it should be readily appreciated thatmulti-component monofilament cutting lines in accordance with thepresent invention may be provided with more than three componentmaterials (i.e. a fourth component material, a fifth component material,etc.).

[0069] Concerns regarding delamination between the various componentmaterials, as discussed hereinabove may also be addressed using the samemechanical or chemical methods suggested. Thus, adjacent componentmaterials within a cutting line may be mechanically interlocked, i.e.,by employing special extrusion techniques utilizing recesses andflanges, and/or may be chemically bound to one another, i.e., byincorporating coupling agents, adhesive-type additives, or ionicfunctionalities into the component material.

[0070] In yet another embodiment of the present invention, the shapedcutting line concept need not be applied to provide an improved cuttingline. Rather, this embodiment focuses on the provision of a high densitycomponent material within a multi-component cutting line. However, aswill be readily apparent from description hereinbelow, shaped cuttingline may also advantageously employ high density component materialsaccording to this present embodiment.

[0071] The high density component material may be distributed throughoutthe core component material and may include, generally, any materialhaving a higher specific gravity than the base material being used foruse in a cutting line. Without wishing to be limited to any particularmaterial, the high density component material will typically be a highdensity polymer or a polymer including fillers so as to increase thespecific gravity of the component material. Useful common non-limitingexamples of high density polymers suitable for use in accordance withthis concept of the present invention include various high molecularweight nylon terpolymers. Useful non-limiting examples of fillersuitable that may be incorporated into polymers, whether of high densityor not, so as to increase the specific gravity of the component materialinclude, inter alia, barium sulfate, zinc oxide or other heavy metalssuch as lead, iron, aluminum, nickel, tungsten, copper and zinc. Forexample, the core component material of a cutting line can obtain arelatively high density by filling the polymer matrix forming the corewith tungsten or barium sulfate at 50 wt/wt %. The core componentmaterial would then be surrounded with a tougher component material suchas nylon 6/66 or similar polymer or copolymer, and, if desired, thistougher component material may be surrounded by another componentmaterial, perhaps, as mentioned above, a smoother component material, tominimize damage to the head of the rotary trimmers in which the cuttingline would be used.

[0072] The advantage of the high density component material is that itprovides greater mass in the same resulting diameter of conventionallines, thereby improving the performance of the cutting line in cuttingthe blades of grass or other vegetation. The increased performance isdue to the fact that, the force of the resulting impact of the cuttingline on the vegetation will increase linearly with the increase indensity of the monofilament. This is based upon the well known principalthat force equals mass times acceleration, F=ma. Consequently, atwo-fold increase in density would result in a two-fold increase in theforce impacted on the vegetation. This is believed to result in fasterand more effective trimming or cutting of the vegetation.

[0073] A multi-component aspect could give better inherent quality tothe cutting line inasmuch as it is generally known that the addition ofsome high density type materials could affect the impact or bendrecovery properties of a singularly extruded monofilament. A cuttingline produced with a core component material comprising a high densitycomponent material encapsulated by a tough polymer sheath may produce asuitably tough monofilament cutting line with increased density.

[0074] Thus, according to this embodiment of the present invention, amulti-component monofilament cutting line is provided having at leasttwo component materials, wherein one component material is a componentmaterial having a high specific gravity. Where the base polymer used innylon, it is known that nylon 6 and nylon 6/66 have a specific gravityof about 1.15 g/cc. Accordingly, any filler or component material havinga specific gravity greater than 1.15 g/cc would be suitable for thepresent invention.

[0075] As mentioned, the increased density of one of the componentmaterials results in an increase in the force impacted on the vegetationbeing cut by the cutting line, although the diameter of the cutting lineof this embodiment may remain substantially identical to conventionalcutting lines. Additionally, by employing a high density componentmaterial, it may be possible to dictate the orientation of the cuttingline's leading edge as the cutting line is spun by a rotary trimmer tocut down vegetation.

[0076] With reference to FIG. 6, it can be seen that a monofilamentcutting line according to this embodiment of the present invention isdesignated generally by the numeral 70. Cutting line 70 includes firstcomponent material 72, which asymmetrically (with respect to itscross-section) defines a portion of the core of cutting line 70, andsecond component material 74, which surrounds first component material72 and, thus, provides a sheath. First component material 72 has aspecific gravity higher than the second component material, while thesecond component material 74 is preferably tough and wear resistant asdisclosed above with respect to other embodiments.

[0077] Notably, first component materials 72 and second componentmaterial 74 are asymmetrical with each other, although the presentinvention should not be limited thereto or thereby. By positioning thehigh density first component material 72 to the rear of the center axisof the cutting line 70 with respect to the direction of movement ofcutting line 70 as delineated by the arrow A, first component material72 weighs cutting line 70 such that leading edge 76 provided by secondcomponent material 74 and containing the tough, impact resistantmaterial will be the first portion of cutting line 70 to impact thevegetation being cut.

[0078] Similarly, in FIG. 7, a bi-valve construction of a cutting line,generally denoted by the numeral 80, is shown. Here, first componentmaterial 82 forms the tail of cutting line 80 while second componentmaterial 84 comprises the body of cutting line 80. First componentmaterial 82 is of high density, and second component material 84 istough and wear resistant. Like FIG. 6, by positioning the high densityfirst component material 84 behind the center axis of cutting line 80with respect to the direction of movement of cutting line 80 asdelineated by the arrow A, the material 82 will weight cutting line 80so that leading edge 86 of the tough second component material willimpact vegetation first. It is also envisioned that cutting lines, suchas cutting lines 70 or 80, could be sheathed or color-coded for ease ofinsertion of the cutting line into the head of the rotary trimmer.

[0079] Conventional nylon monofilament cutting lines typically have aspecific gravity of about 1.15 g/cc or less. However, in this embodimentof the present invention, the high density component material, whetherfilled or unfilled, preferably has an overall specific gravity greaterthan about 1.15 g/cc. Thus, the multi-component cutting line will alsohave a specific gravity of greater than 1.15 g/cc.

[0080] Having described the high density component material embodimentof the present invention, it should be readily apparent that thisconcept can be applied in any of the embodiments previously disclosed ordisclosed hereinbelow. For example, the cutting lines of FIGS. 1-5 couldcontain a high density component material at their cores so as toincrease the force of impact on vegetation being cut by the cuttingline, while the diameter of the cutting line may remain substantiallyidentical to conventional cutting lines. Likewise, in the embodimentsdisclosed hereinbelow, it should be readily apparent how a high densitycomponent material may advantageously impact the function of the cuttingline.

[0081] Fillers may also advantageously be employed for purposes otherthan increasing the density of a component material. Particularly, acomponent material may be filled with an abrasive material serving toprovide the component material with a more aggressive cutting edge.Thus, in still another embodiment of the cutting line of the presentinvention, the concept of using a smooth, softer outer sheathsurrounding a harder, more abrasive core or mantle material ismaintained as described above. As shown in FIG. 8, a monofilamentcutting line 90 includes first component material 92, second componentmaterial 94, and third component material 96, which can be considered ascore, mantel, and sheath layers, respectively. The first componentmaterial 92 and third component material 96 may, respectively, includeany of the materials or configurations disclosed herein with respect tovarious core and sheath layers of a cutting line. Second componentmaterial 94, however, contains abrasive material 98. It will beappreciated that abrasive material 98 could instead or in addition beemployed in the core (i.e. first component material 92) of cutting line90 without the need for a mantle layer (i.e. second component material94), or in more than one mantle layer. Nevertheless, where used,abrasive material 98 is distributed throughout.

[0082] Abrasive material 98 can be essentially any abrasive known in theart and is preferably grit material. Grit material may include, interalia, silica dioxide, sand, and titanium nitride. Generally, thesematerials are relatively large particles. The advantage of usingabrasive materials 98 is that it provides a more aggressive cuttingedge, thereby improving the performance of a cutting line in cuttingvegetation.

[0083] During use, third component material 96 (i.e. the sheath) wouldbe worn away while performing an initial cutting. This would exposesecond component material 94 containing abrasive materials 98. Thus,third component material 96 (sheath) can be either a polymer commonlyused in the manufacture of cutting lines or a less hard and less toughpolymer such as a low molecular weight polyamide or polyolefin, asdescribed above. Where a softer, easily removed outer sheath isemployed, it is generally preferred that the abrasive type material bedistributed throughout the mantle (e.g. second component 92) and thatthe core include a tough, impact resistant polymer commonly used in theproduction of cutting line. Again, concerns regarding delamination ofthe core from the mantle or sheath can be addressed as described above.Additionally, the same techniques can be used to improve the adhesion ofthe grit material to the surrounding polymer matrix.

[0084] In addition, it is envisioned that the core material itself canbe used as the abrasive material. It is well known that some of thepolymers commonly used in the production of monofilament, when leftslightly wet, will incur bubbles after being extruded through the diehead. It is believed a roughened surface formed by the rupture of thesebubbles could also be used as an embedded abrasive. Indeed, such bubblesand roughened surfaces are to be considered “abrasive material” forpurposes of the present invention.

[0085] In order to demonstrate practice of the present invention,several studies have been conducted. Most pertinent of these is believedto be the test related to wear resistance. Here, a number of singlecomponent monofilament cutting lines and multi-component monofilamentcutting lines having the same specific gravity and the samecross-sectional configuration were tested. One multi-componentmonofilament cutting line employed a first material of conventionallyextruded nylon 6/66 sheathed by a second component material of speciallyprocessed and extruded nylon 6/66. This cutting line was compared to aconventionally extruded nylon 6/66 cutting line as well known in theart. In the test, cutting was done on a 1200 square foot grass field.The amount of cutting used was then determined. In this case, themulti-component cutting line cut about 3200 square feet of grass perinch of cutting line worn. This compared to only about 550 square feetof grass per inch of cutting line worn for the control.

[0086] In another instance, a multi-component monofilament cutting lineemployed a first material of conventionally extruded nylon 6 sheathed bya second component material of specially processed and extruded nylon 6.This cutting line was compared to a conventionally extruded nylon 6cutting line. In this case, the multi-component cutting line cut about980 square feet per inch of cutting line worn, while the conventionalnylon 6 cutting line cut only 235 square feet per inch of cutting lineworn. Clearly, there was a significant increase in the wear resistanceof the multi-component cutting line.

[0087] Thus, it should be evident that the various embodiments ofcutting lines of the present invention are highly effective in improvingthe grass cutting performance over known cutting lines. It should beappreciated that each of the embodiments disclosed hereinabove may beemployed separately or may be employed in combination with otherembodiments herein disclosed. Thus, shaped cutting lines includingcomponent materials providing cutting edges having better wear andabrasion resistant properties than other component materials within thecutting line may, optionally, include high density component materialsand/or component materials including abrasive materials. Likewise, acutting line including a high density component material may optionallyinclude component material providing cutting edges having better wearand abrasion resistant properties than other components within thecutting line, may include recessed edges, may include a smoothprotective sheath component material, and/or may include a componentmaterial including an abrasive material. Indeed, it should be readilyapparent that each embodiment of the present invention may be employedseparately or together with any number of other embodiment disclosedherein. The invention is particularly suited for use in rotary trimmershaving a rotating head, but is not necessarily limited thereto. Thecutting lines of the present invention can be used separately or withother equipment, methods and the like.

[0088] Based upon the foregoing disclosure, it should now be apparentthat the use of the extruded multi-component monofilament as avegetation cutting line as described herein will carry out the objectsset forth hereinabove. It is, therefore, to be understood that anyvariations evident fall within the scope of the claimed invention andthus, the selection of specific component elements and cross sectionalshapes of the monofilament can be determined without departing from thespirit of the invention herein disclosed and described. In particular,the cross-sectional configurations of each monofilament, as well as thecore, the mantle or the sheath thereof, according to the presentinvention are not necessarily limited to those shown in the drawings.Any shaped monofilament cutting line and capable of being extruded as ashaped multi-component monofilament can be employed. Moreover, as notedhereinabove, compositional ingredients other than those particularlyspecified in this description can be substituted for those identified,provided that they can be extruded. Thus, the scope of the inventionshall include all modifications and variations that may fall within thescope of the attached claims.

What is claimed is:
 1. A extruded monofilament cutting line for a rotarytrimmer for cutting vegetation comprising: a first component material;and a second component material extruded separately from said firstcomponent material, said second component material providing the cuttingline with cutting edges, wherein said second component material hasincreased wear resistance properties and increased abrasion resistanceproperties compared to those same properties of said first componentmaterial and wherein said second component material is selected fromionomer resins, and blends and mixtures of polymers with the ionomerresins.
 2. A monofilament cutting line as in claim 1, wherein said firstcomponent material has an increased impact strength as compared to theimpact strength of said second component material.
 3. A monofilamentcutting line as in claim 1, wherein said second component material has awear resistance at least twice as great as the wear resistance of saidfirst component material.
 4. A monofilament cutting line as in claim 1,wherein said first component material forms at least a portion of a coreof the cutting line, and wherein said second component material forms asheath around said first component material.
 5. A monofilament cuttingline as in claim 1, wherein said second component material is used onlyin the formation of the cutting edges and does not form a sheath aroundsaid first component material.
 6. A monofilament cutting line as inclaim 1, wherein said first component material and said second componentmaterial are made from a same or polymers selected from the groupconsisting of polyolefins, polyamides, polyimides, and polyurethanes,and copolymer, terpolymer and ionomer blends thereof.
 7. A monofilamentcutting line as in claim 6, wherein said first component material isnylon 6/66 and said second component material is a blend of nylon 6/66and an ionomer resin.
 8. A monofilament cutting line as in claim 1,wherein said first component material has a specific gravity greaterthan the specific gravity of said second component material.
 9. Amonofilament cutting line as in claim 8, wherein said second componentmaterial includes nylon having a specific gravity of about 1.15 g/cc andsaid first component material has a specific gravity greater than about1.15 g/cc.
 10. A monofilament cutting line as in claim 8, wherein saidfirst component material and said second component material areasymmetrically positioned in cross section with respect to each other.11. A monofilament cutting line as in claim 10, wherein said firstcomponent material is positioned substantially behind said secondmaterial, thereby dictating a leading edge of the cutting line as beingthat formed by said second component material.
 12. A monofilamentcutting line as in claim 1, wherein said first component material ismechanically bound to said second component material.
 13. A monofilamentcutting line as in claim 1, wherein said first component material ischemically bonded to said second component material.
 14. A monofilamentcutting line as in claim 1, wherein said second component materialincludes Suryln®.